The Department Chair Is Out of Town at a Conference

The department chair is out of town at a conference and you, as the assistant department chair, find yourself besieged by dozens of students needing permission to get into a very popular (but closed) class. Student arrivals are governed by the Poisson distribution with a mean of 10 minutes. Telling the students that they can't get into the closed class takes about 5 minutes, and this average is exponentially distributed. About how long do students wait outside your office door?

A) 0.083 minutes
B) 0.083 hours
C) 0.50 minutes
D) 0.50 hours